Need help with 2 Energy and Work related physics problems?

Question

Need help with 2 physics problems.?
For number 3 i have found part a i just need part b.
3. A ski starts from rest and slides down a 26° incline 70 m long. Use energy methods.
(a) If the coefficient of friction is 0.09, what is the ski's speed at the base of the incline?
22.1 m/s
(b) If the snow is level at the foot of the incline and has the same coefficient of friction, how far will the ski travel along the level?
______ m

6. If you stand on a bathroom scale, the spring inside the scale compresses 0.50 mm, and it tells you your weight is 700 N. Now if you jump on the scale from a height of 0.80 m, what does the scale read at its peak?
__________ N

SHOW STEPS THAT ARRIVE TO THE ANSWER. This way i can understand what you've did and i can learn from it. Yes, i did post a previous question like this but the person who answered didn't say it clearly, plus the answer is wrong when i solve it his way.

Energy and Work methods mean the formulas having to do with KE, PE, and Work=Fd

2nd response's answer is wrong, the number seems too big

I got 3b i just need answer to number 6

Answer 1

For 3b, just use W=Fd-- since work is equal to the change in energy of the system-- you know that when the ski stops, it will have zero kinetic energy. And, you know the force of friction that's going to act on the ski. So, the work is going to be equal to the kinetic energy at the bottom of the incline. Just divide KE/F=d. And, since both are proportional to m, you don't need to know the mass of the ski...

Number 6--First use F=-kx to find the spring constant of the scale. Then use conservation of energy-- at the beginning, you just have gravitational potential energy. At the end, you just have energy stored in the spring-- E=(1/2)kx^2. Just set mgh=(1/2)kx^2, and solve for x. Then, I'd assume that the spring is linear and plug that x into f=-kx, getting out f (which should correspond to the maximum reading on the scale).

Note: don't forget to figure out your mass in kg from the reading on the scale...

Answer 2

huggh all i know in physics is
f=ma
momentum=mass* velocity
v=u+at
s =ut+half at2
v2 =u2 +2as
do allu can do with that